Calculating your basal metabolic rate (calories at rest)
Medical review in progress.
The basal metabolic rate is the energy spent at rest for vital functions. Mifflin-St Jeor (American Journal of Clinical Nutrition, 1990): man = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5; woman = the same calculation − 161. The result is in kilocalories per day.
The calculation runs in your browser. No data is sent or stored.
Example: a woman aged 40, 65 kg (143 lb) and 165 cm (5 ft 5 in). Mifflin-St Jeor: 10 × 65 + 6.25 × 165 − 5 × 40 − 161 = 1 320 kcal per day. Revised Harris-Benedict (Roza and Shizgal, equation on all series): 1 387 kcal per day.
Calculating your basal metabolic rate
The calculator is free. It asks for sex, weight, height and age, then shows two estimates. Nothing is sent. It does not apply before 18: the equations cited were established in adults.
Mifflin and colleagues measured resting expenditure by indirect calorimetry in 498 adults aged 19 to 78. The equation simplified by sex has the same predictive power as the full form (R² = 0.71).
The formulas used and their limits
Mifflin-St Jeor, man: 10 × weight + 6.25 × height − 5 × age + 5. Woman: 10 × weight + 6.25 × height − 5 × age − 161. Weight in kilograms, height in centimeters, age in years. The form on this page also accepts pounds, feet and inches, and converts them before the calculation.
Revised Harris-Benedict, Roza and Shizgal, 1984, equations computed on all series (men n = 168, women n = 169). Man: 88.362 + 4.799 × height + 13.397 × weight − 5.677 × age. Woman: 447.593 + 3.098 × height + 9.247 × weight − 4.330 × age. In the article, height is in centimeters: their example, a man of 170 cm (5 ft 7 in), 70 kg (154 lb) and 50 years, gives 1 558 kcal with this equation. The published 95 % confidence interval is about ± 213 kcal for men and ± 201 kcal for women.
The same study recalls that the 1919 equations estimate the expenditure of a normally fed subject with an accuracy of about 14 %, and that they are unreliable in undernutrition. This calculator does not cover the Black et al. formula: its coefficients are not reproduced here.
If lean mass is known, Mifflin also publishes: resting expenditure = 19.7 × lean mass (kg) + 413. This calculator asks for neither fat mass nor lean mass.
From basal metabolic rate to calorie needs
The figure shown is a resting expenditure, not the day's expenditure. Walking, working and digesting add to it. This page does not multiply the result by an activity factor: neither Mifflin nor Roza publish the 1.2 / 1.375 scale often copied online.
For the day, the reference remains a professional, with the real activity level. A structured program exists on the site; it does not replace this calculation.
Basal metabolic rate for women and men
At identical weight, height and age, the women's formula is 166 kcal lower than the men's formula (5 − (−161)). This is not a population average. There is no “average” basal metabolic rate for a woman on this page: the figure is calculated for one person.
The page's example, 65 kg (143 lb), 165 cm (5 ft 5 in), 40 years, gives 1 320 kcal (Mifflin) and 1 387 kcal (Roza). A man of 80 kg (176 lb), 180 cm (5 ft 11 in) and 35 years gives 1 755 kcal (Mifflin).
What makes the metabolic rate vary
In both formulas, weight and height increase the result, age decreases it. In Mifflin, each additional year removes 5 kcal, at unchanged weight and height. This is not a measurement of your metabolism: it is the age term of the equation.
Lean mass is, in Mifflin's article, the best single predictor of resting expenditure. Total weight is less so, because it mixes muscle and fat.
Metabolic rate and weight loss
Eating less than your basal metabolic rate is not advice from this page. Resting expenditure covers functions that do not stop. A deficit, if considered, is discussed above this floor, with a professional.
The calculator proposes no target intake for losing weight. It gives two estimates of rest, with their margin.
This information does not replace the advice of a healthcare professional.
Frequently asked questions
How do you calculate your basal metabolic rate?
From weight, height, age and sex. Mifflin-St Jeor: man = 10 × weight + 6.25 × height − 5 × age + 5; woman = the same calculation − 161. This page also shows Harris-Benedict revised by Roza and Shizgal.
What is the average basal metabolic rate of a woman?
This page publishes no average. The result depends on weight, height and age. The example of a woman aged 40, 65 kg (143 lb) and 165 cm (5 ft 5 in) gives 1 320 kcal per day with Mifflin-St Jeor.
Does the basal metabolic rate fall with age?
In these formulas, yes: Mifflin removes 5 kcal per year, at identical weight and height. It is a term of the equation, not a personal measurement.
Should you eat less than your basal metabolic rate to lose weight?
No. This page does not recommend an intake below resting expenditure. Any deficit is looked at with a professional, above this level.
Which formula is the most reliable?
Mifflin-St Jeor was established on 498 adults and indicates that the 1919 Harris-Benedict equations overestimated measured expenditure by about 5 %. Roza and Shizgal give a revision, with an interval of about ± 200 kcal. Both remain estimates.
Is the calculation free?
Yes. It runs in the browser, with no account. No value is sent or kept.
Can the basal metabolic rate be calculated from fat mass?
Not here. Mifflin publishes a separate equation from lean mass: 19.7 × lean mass + 413. It is not in the form.
Sources
Read also
The formula estimates, it does not measure. Vita measures lean mass and fat mass. This calculator uses only weight, height, age and sex. See the Vita scale